Read the job descriptions carefully
The general job description is complemented by role-specific job descriptions for all courses looking for TAs. As what is expected from a TA differ from course to course, it is important to read the role-specific job descriptions carefully.

Read the course descriptions
It is also important to read the course description for the course you are interested in TA’ing for – maybe the course changed from when you took it. 

Check the schedule
Finally, it is important to check the schedule of the course(s) you are interested in TA’ing for so that it doesn’t clash with any of your other obligations. It is also important to consider the course schedules if applying for 2 or more courses.